Search

In chronic lymphocytic leukemia (CLL), there is a growing interest for minimal residual disease (MRD) monitoring, due to the availability of drug combinations capable of unprecedented complete clinical responses. The standardized and most commonly applied methods to assess MRD in CLL are based on flow cytometry (FCM) and, to a lesser extent, real-time quantitative PCR (RQ-PCR) with allele-specific oligonucleotide (ASO) primers of immunoglobulin heavy chain genes (IgH). Promising results are being obtained using droplet digital PCR (ddPCR) and next generation sequencing (NGS)-based approaches, with some advantages and a potential higher sensitivity compared to the standardized methodologies. Plasma cell-free DNA can also be explored as a more precise measure of residual disease from all different compartments, including the lymph nodes. From a clinical point of view, CLL MRD quantification has proven an independent prognostic marker of progression-free survival (PFS) and overall survival (OS) after chemoimmunotherapy as well as after allogeneic transplantation. In the era of mechanism-driven drugs, the paradigms of CLL treatment are being revolutionized, challenging the use of chemoimmunotherapy even in first-line. The continuous administration of ibrutinib single agent has led to prolonged PFS and OS in relapsed/refractory and treatment naïve CLL, including those with TP53 deletion/mutation or unmutated IGHV genes, though the clinical responses are rarely complete. More recently, chemo-free combinations of venetoclax+rituximab, venetoclax+obinutuzumab or ibrutinib+venetoclax have been shown capable of inducing undetectable MRD in the bone marrow, opening the way to protocols exploring a MRD-based duration of treatment, aiming at disease eradication. Thus, beside a durable disease control desirable particularly for older patients and/or for those with comorbidities, a MRD-negative complete remission is becoming a realistic prospect for CLL patients in an attempt to obtain a long-lasting eradication and possibly cure of the disease. Here we discuss the standardized and innovative technical approaches for MRD detection in CLL, the clinical impact of MRD monitoring in chemoimmunotherapy and chemo-free trials and the future clinical implications of MRD monitoring in CLL patients outside of clinical trials.

Chronic lymphocytic leukaemia (CLL) is uncommon in Chinese population and its biology, genetics and treatment outcome in Chinese patients have not been comprehensively investigated. In this study, we studied the clinicopathological features and outcome of 212 Chinese patients with newly diagnosed CLL in Hong Kong and Singapore. The median age at diagnosis was 64 years. The majority of patients presented with early-stage disease (Binet stage A, 56.1%). Del(13)(q14) was the most frequent abnormality (41.7%) detected by fluorescence in situ hybridization (FISH) analysis. Del(17p) and TP53 gene mutations were detected in 7.8% and 8.2% of patients, respectively. MYD88 mutations were found at a higher frequency (11.5%) than expected. CLL with unmutated variable region of the immunoglobulin heavy chain genes (IGHV) occurred in only 31.2% of cases, and was associated with advanced-stage disease (p <0.01) and adverse FISH abnormalities (p<0.01). With a median follow-up of 39 months, the median overall survival (OS) was 108 months. The presence of del(17p) or TP53 mutations was associated with a significantly shorter time to first treatment and an inferior OS (p <0.01). Unmutated IGHV was also associated with a significantly shorter time to treatment (p <0.01). Among patients who required treatment, the median OS and progression-free survival (PFS) were 107 and 23 months, respectively. The presence of del(17p) was associated with a significantly inferior OS and PFS (p <0.01). In summary, Chinese CLL patients had similar genetic aberrations at diagnosis compared with those of Western populations. FISH abnormalities are major factors affecting outcome.

Chronic lymphocytic leukemia (CLL) is the most common type of leukemia in the Western world, whereas in Asia the incidence is about 10 times lower. The basis for this ethnic and geographic variation is currently unknown. The aim of this study was to characterize IGHVDJ rearrangements and stereotype of the HCDR3 region in a series of 623 Chinese CLL, in order to identify possible differences in immunoglobulin gene usage and their potential pathogenetic implications. Chinese CLL were compared to 789 Italian CLL. Chinese patients showed a higher proportion of mutated IGHV and a more frequent usage of IGHV3-7, IGHV3-74, IGHV4-39 and IGHV4-59 genes. A significantly lower usage of IGHV1-69 and IGHV1-2 was documented, with comparable IGHV3-21 frequency (3% Chinese vs 3.8% Italian CLL). The proportion of known stereotyped receptors was significantly lower in Chinese (19.7%) than in Italian CLL (25.8%), despite a significantly higher frequency of subset #8 (p= 0.0001). Moreover, new paired clusters were identified among Chinese cases. Overall, these data support a potential different antigenic exposure between Eastern and Western CLL.

Chronic lymphocytic leukemia (CLL) with stereotyped B-cell receptor (BCR) belonging to subset #1 (IGHV1-5-7/ IGKV1-39) display a poor outcome. To characterize their genetic and genomic features and BCR function, we selected 20 subset #1 CLL from a series of 579 cases. Subset #1 CLL, all showing unmutated IGHV, were associated with the presence of del(11q) (50%) in comparison with unmutated CLL, unmutated stereotyped CLL other than subset #1 and with cases using the same IGHV genes but a heterogeneous VH CDR3 (non-subset #1 CLL). There were no distinctive features regarding CD38, ZAP-70, and TP53 disruption. NOTCH1, SF3B1, and BIRC3 were mutated in 15%, 0%, and 5% of cases, respectively, while BIRC3 was deleted in 22% of cases. Microarray unsupervised analysis on 80 unmutated/mutated/stereotyped/non-stereotyped CLL showed a tight clustering of subset #1 cases. Their genomic signature exhibited several differentially expressed transcripts involved in BCR signal transduction, apoptosis regulation, cell proliferation, and oxidative processes, regardless of del(11q). Accordingly, BCR ligation with anti-IgM revealed a significant higher proliferation of subset #1 versus unmutated non-subset #1 CLL, both at baseline and after 24–48 hr stimulation. Subset #1 CLL represent a paradigmatic example of the direct link between BCR structure, function, and patients prognosis.